Astronomy and Astrophysics – Astrophysics – Earth and Planetary Astrophysics
Scientific paper
2011-08-22
Astronomy and Astrophysics
Astrophysics
Earth and Planetary Astrophysics
36 pages, 9 figures, accepted for publication in ApJ
Scientific paper
We present an improved formula for the anomalous radial velocity of the star during planetary transits due to the Rossiter-McLaughlin (RM) effect. The improvement comes from a more realistic description of the stellar absorption line profiles, taking into account stellar rotation, macroturbulence, thermal broadening, pressure broadening, and instrumental broadening. Although the formula is derived for the case in which radial velocities are measured by cross-correlation, we show through numerical simulations that the formula accurately describes the cases where the radial velocities are measured with the iodine absorption-cell technique. The formula relies on prior knowledge of the parameters describing macroturbulence, instrumental broadening and other broadening mechanisms, but even 30% errors in those parameters do not significantly change the results in typical circumstances. We show that the new analytic formula agrees with previous ones that had been computed on a case-by-case basis via numerical simulations. Finally, as one application of the new formula, we reassess the impact of the differential rotation on the RM velocity anomaly. We show that differential rotation of a rapidly rotating star may have a significant impact on future RM observations.
Albrecht Simon
Hirano Teruyuki
Narita Norio
Sato Bun'ei
Suto Yasushi
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